Flexible slabstock polyurethane foam for furniture and bedding has traditionally been produced using toluene diisocyanate (TDI) as a basic raw material. In the United States, methylene diphenyl diisocyanate (MDI) has predominantly been used in polyurethane foam applications other than flexible slabstock polyurethane foam applications such as furniture and bedding. MDI has been used in, for example, molded polyurethane foam such as automotive applications; rigid polyurethane foam such as insulation, construction and packaging; microcellular froth polyurethane foam such as footwear and gasketing; and viscoelastic (“memory”) polyurethane foam chemistries. Due in part to the inherently different chemical reaction kinetics as well as the differences in foam stabilization requirements for processing using MDI as opposed to TDI, MDI does not readily fit the criteria for use in continuous flexible slabstock foam formulations. In Europe, MDI has only recently been utilized to produce high density, namely greater than 2.5 pounds per cubic foot (PCF) high resilience slabstock foams. In general terms, the complexity of formulation, speed of reactivity and mechanical processing limitations have prevented the commercialization of low density, soft MDI-based foams since the advent of the flexible polyurethane foam industry in the 1950s. Furthermore, the furniture and bedding markets in the United States use a larger volume of non-high resilience, also referred to as conventional, flexible polyurethane foam relative to the European foam market.
In the wake of Hurricane Katrina in the United States, many of the necessary flexible polyurethane foam raw materials became temporarily but seriously unavailable due to unplanned chemical plant shutdowns and transportation problems. More recently, a similar situation with TDI specifically, due to global demand exceeding current supply, resulted in allocated supply and significant price increases.
The cost of polyurethane foam, whether TDI or MDI-based, is driven almost solely by chemical cost. Lower density foams cost less per unit volume than higher density foams, making them more attractive to end users, given acceptable performance. In the United States market, where foam is considered commodity-like, due to similarity of product and aggressive pricing, high-density European-style MDI foams have never widely gained acceptance.
Thus, there is a need to reduce dependence on potentially scarce raw materials to produce a MDI-based conventional flexible polyurethane foam, more particularly one that is acceptable to the particular needs of the furniture, bedding and other industries. Accordingly, there is a need for an alternative low-density conventional flexible slabstock polyurethane foam.